Five changes made it much easier to fit the engine in the cowl-

1) I put the prop flange at 44" forward of the firewall, instead of 39". I put the heat exchangers under the main spar to put some weight back a bit to even out the CG. I will do the weight and balance soon, and change the battery position if needed. I don't think it will be.

2) I used a 16" dia spinner, which allows a slightly wider and taller cowl, especially in the forward part of the cowl. It looks really nice, too.

3) I raised the firewall 1" by making a new portion that goes from the top of the engine mount up. This gives a little more room up top.

4) The cowl goes two inches deeper- lower on the bottom. That allows me space to put a muffler under the fuselage, and run the oil and coolant lines under the fuselage. I put a lot of heat sheilding and protection for the coolant lines under there because of the muffler. The muffler and lines are completely enclosed under the fuselage for streamlining. There are provisions for venting- three NACA ducts on the forward part of the cowl, spaced 120 degrees apart, one on the top, two on the sides. The top one provides a blast tube for the alternator, the left side feeds into a plenum that surrounds the exhaust system, and the right side provides a blast tube that blows over the coils that are mounted next to the engine. I am going to put a reverse scoop at the exhaust outlet to pull air through the cowl and over the muffler.

5) I chose to make an aluminum cowl so that I wouldn't worry about burning a fiberglass cowl. Material costs for the cowl were under $300, not counting the purchase of an english wheel ~ $350, and the several previous practice attempts at a cowl.

I'm  really happy with the results, it gets a lot of positive comments.

I'm waiting for my registration application to come back from Oklahoma, then will be looking at an inspection.

I was running the engine up yesterday, doing a little taxiing around. Tracy's EM2 shows 151 HP at 4550 RPM static, I didn't give it any more throttle, there was a bit more left. I have the 2.85/1 redrive, so would expect around 6800 at cruise. The prop is a Catto 74" dia x  88 pitch. Compression is 9.1/1 I think, this was a turbo engine, but is now N/A  If the torque curve was completely linear, and the EM2 reflects a true HP value, then I should get around 225 HP at 6800 rpm. If this is the case, then I will have exceeded my expectations by around 35 HP.  It's probably too good to be true. In any case, I'm not disappointed with this engine.


Brian Trubee